EP0931771A1 - Methode for manufacturing of a matrix for monomode fibres - Google Patents

Abstract

Fabrication of fibre optic matrices comprises: arranging fiber optics in an enclosure in the form of a deformable parallelogram, in a matrix made up of rows and columns forming an angle between them and deforming the enclosure in order to vary the angle.

Description

The invention relates to the manufacture of matrices for optical fibers, in particular single-mode.

• port d'entrées et sorties pour les commutateurs et brasseurs optiques en espace libre ;
• réalisation de matrices de faisceaux collimatés en association avec des matrices de microlentilles ;
• réalisation de connecteurs 2D haute densité pour bus optique ; et
• couplage de matrices de VCSEL (Vertical Cavity surface Emetting Laser) avec des matrices de fibres monomodes.

The availability of single-mode optical fiber arrays represents an important challenge for the development and popularization of optical technologies, essentially in two fields which are: on the one hand switching and optical patching systems in free space with high density of interconnections , and secondly the backplane connections and the integration of components with fiber matrices. Single-mode fiber matrices are key and essential components for these two fields of activity and perform the following functions:

• input and output ports for free space optical switches and mixers;
• production of collimated beam arrays in association with microlens arrays;
• production of high density 2D connectors for optical bus; and
• coupling of VCSEL (Vertical Cavity surface Emetting Laser) matrices with single-mode fiber matrices.

The assembly of single-mode fibers with the required specifications, i.e. accuracy of positioning of the order of µm between fibers exists under shape of bars. The fibers are placed in "V" grooves made by etching on substrate of silicon or by machining on a glass or zirconium support. Commercial products are currently available.

However, with regard to the assembly of fibers in matrices, the realization remains delicate and some unresolved issues to date. The solution which would consist of stacking bars is to be excluded because of the impossibility of controlling the thickness of these bars with an accuracy of the order of µm.

(A) N. BASAVANHALLY and al, "Evaluation of Fiber Arrays for Free Space Interconnect Applications", International Topical Meeting on OPTICAL COMPUTING, Salt Lake City, UTAH, USA, 15-17 March 1995, Vol. 12, PFB2-1, pp. 124-128 ;

(B) GEOFF M. PROUDLEY, C. STACE, H. WHITE, "Fabrication of two Dimensional Fiber Optic Arrays for an Optical Crossbar Switch" OPTICAL ENGINEERING, February 1994, Vol. 33, No. 2, pp. 627-635 ;

(C) J.M. SASSIAN and al., "Fabrication of Fiber bundle Arrays for Free-Space Photonic Switching Systems", OPTICAL ENGINEERING, September 1994, Vol. 33, No. 9, pp. 2979-2985.

Two avenues are currently being explored. The first resides in the dynamic positioning of the fibers using a piezoelectric micro-positioner in a matrix of holes which can be produced according to various methods such as etching on silicon substrate, precision drilling or ablation of metal by laser. However, this technique, which consists in carrying out an individual and dynamic alignment and bonding of the fibers in a matrix of holes, is delicate, long and very expensive. In addition, it does not have all the guarantees of a good angular positioning of the fiber in its support and of perfect parallelism between the axes of the fibers. The precision of the positioning of the fibers is determined by the regularity of the pitch and the diameter of the holes in the matrix as well as the performance of the micropositioner. In this regard, reference is made in particular to the following documents:

(A) N. BASAVANHALLY and al, "Evaluation of Fiber Arrays for Free Space Interconnect Applications", International Topical Meeting on OPTICAL COMPUTING, Salt Lake City, UTAH, USA, 15-17 March 1995, Vol. 12, PFB2-1, pp. 124-128;

(B) GEOFF M. PROUDLEY, C. STACE, H. WHITE, "Fabrication of two Dimensional Fiber Optic Arrays for an Optical Crossbar Switch" OPTICAL ENGINEERING, February 1994, Vol. 33, No. 2, pp. 627-635;

(C) JM SASSIAN et al., "Fabrication of Fiber bundle Arrays for Free-Space Photonic Switching Systems", OPTICAL ENGINEERING, September 1994, Vol. 33, No. 9, pp. 2979-2985.

In a second technique, we perform a stack of bare fibers or positioned in microferrules in a U-shaped support. This technique, which consists of making a stack of ferrules inside of which the fibers are found in a rigid structure in the shape of "U", is an assembly collective with good angular positioning, but presents a perpendicularity defect of the matrix of ferrules, therefore too large a position error for fibers located in the corners with respect to a reference grid. We will refer in particular to document (D) K. KOYABU, F. OHIRA, T. YAMAMOTO, "Fabrication of Two-Dimensional PANDA Fiber Array Digital Free-Space Photonic Switch Module ", International Topical Meeting on OTICAL COMPUTING, Sendai, JAPAN, 21-25 April 1996, Technical Digest Vol. 1, PWC26, pp. 136-137.

An object of the invention is to provide a method of simple, fast and low-cost fiber matrix manufacturing expensive to implement, and making it possible to manufacture a fiber matrix with good perpendicularity between rows and columns, and a good parallelism between the axes of the fibers.

• disposer des fibres optiques dans une enceinte en forme de parallélogramme déformable, en une matrice comprenant des lignes et des colonnes formant un angle par rapport aux lignes ; et
• déformer l'enceinte pour faire varier l'angle.

With a view to achieving this aim, a method of manufacturing optical fiber arrays is provided according to the invention, comprising the steps consisting in:

• arranging the optical fibers in an enclosure in the form of a deformable parallelogram, in a matrix comprising lines and columns forming an angle with respect to the lines; and
• deform the enclosure to vary the angle.

Thus, this process makes it possible to optimize the perpendicularity of the sides of the matrix. The process of the invention allows the production of fiber matrices with a position deviation of each fiber core less than +/- 2.5 µm compared to a grid predetermined according to the chosen pitch, and a angular misalignment not exceeding +/- 5 milliradians. These tolerances make it possible to obtain coupling losses between single-mode fibers less than 3 dB. Thanks to this process, the realization fiber matrices, in particular single-mode fibers, is extremely simple. The setting which is collective is done by simple visualization.

The validation of this juxtaposition process and based on the fact that when the assembly, the fibers, and for example the ferrules, are placed randomly. Then there is a balance in the distribution between the ferrules which have maximum and minimum diameter. So every heart of fiber is at a position very close to the grid defined according to the pitch. One in five simulations thousand reconfigurations of an 8x8 matrix (sixty-four fibers) made it possible to verify this analysis. In the case of the least favorable assembly, the average deviation compared to a benchmark grid is only to 2.06 µm.

Advantageously, the method comprises the step of fix the fibers relative to each other.

Advantageously, the fixing step comprises a molding using a resin.

Advantageously, the method comprises the step of press the die in at least one direction from the direction of the rows and the direction of the columns.

Thus, in addition to its perpendicularity, we regulate the dimensions of the matrix.

There is also provided according to the invention a device for manufacturing fiber matrices optical, having four faces defining a enclosure suitable for receiving optical fibers arranged in a matrix, the faces giving to the enclosure a form of parallelogram, non-parallel faces between them forming an angle, in which the enclosure is deformable to vary the angle.

This device makes it possible to implement the method according to the invention.

Advantageously, the device comprises means angle adjustment.

Advantageously, the method comprises two elements forming two sides of the enclosure parallel to each other, a chassis, and at least one actuator movable relative to to the chassis and connected to the elements so that a displacement of the actuator varies the angle.

The actuator allows you to precisely modify the perpendicularity of the parallelogram.

Advantageously, the actuator is articulated to the frame.

Advantageously, the actuator is articulated by means a flexible part.

Advantageously, the device comprises two actuators connected to the two respective elements and interconnected.

Advantageously, the device comprises means for adjusting a distance separating faces of the enclosure parallel to each other.

Advantageously, the means for adjusting the distance include an actuator, a pusher to push one of the faces under the effect of a solicitation by the operating member, and a ball interposed between the operating member and the pusher.

This avoids transmitting a request in rotation on the matrix at the same time as we exercise a push for size adjustment.

Advantageously, the device comprises zirconium elements forming the faces.

Advantageously, the elements include wedges.

A matrix is further provided according to the invention. of optical fibers produced by a process according to the invention.

The invention is particularly advantageous for single-mode fiber matrices.

• la figure 1 est une vue en élévation d'un dispositif de fabrication selon un mode préféré de réalisation de l'invention ;
• la figure 2 est une vue à plus grande échelle d'un détail de la figure 1 ;
• la figure 3 est une vue en coupe transversale d'une matrice de fibres avec un important défaut de perpendicularité ; et
• la figure 4 est une vue de la matrice de la figure 3 après correction du défaut.

Other characteristics and advantages of the invention will become apparent in the following description of a preferred embodiment given by way of nonlimiting example. In the accompanying drawings:

• Figure 1 is an elevational view of a manufacturing device according to a preferred embodiment of the invention;
• Figure 2 is an enlarged view of a detail of Figure 1;
• Figure 3 is a cross-sectional view of a fiber matrix with a significant defect in perpendicularity; and
• Figure 4 is a view of the matrix of Figure 3 after correcting the defect.

Figures 1 and 2 illustrate a mode of preferred embodiment of the device for manufacturing single-mode optical fiber arrays according to the invention. This device comprises a chassis 2 comprising a base 4, here horizontal, and two uprights, here vertical, left and right 6 extending opposite each other perpendicular to the base 4. It has a support 8 fixed to base 4 midway between the uprights, between these.

The device has two straight beams vertical 10 with rectangular section, identical between them, extending through a lower end 12 to from the base 4 parallel to the uprights 6, between these. The device comprises an upper arm 14 connected to upper ends 16 of beams 10. The lower 12 and upper 16 ends of the beams 10 are thinned to form elastically flexible joints. The base 4, the upper arm 14 and the beams 10 are arranged to constitute a deformable parallelogram. The device comprises two micrometric screws 18 mounted in connection screw-nut on upper ends of uprights respective 6 so that the free ends of the screws 18 are oriented towards each other and are adapted to rest on respective ends left and right of upper arm 14 in order to move this one to the left or to the right and so form the parallelogram.

The device comprises a left spacer 20 fixed to a right internal face of the left beam 10, and an upper and straight spacer 22 fixed to a left internal face of the right beam 10. This spacer 22 has a vertical through conduit threaded 24 opening opposite the support 8, and a horizontal threaded through conduit 26 opening into look at the left spacer 20. This conduit 26 is extended by a smooth duct crossing the beam right 10. In each of the two conduits 24, 26 of the spacer 22, the device comprises a pusher respective 28 with smooth external face, engaged in the conduit, and an actuator 30 with a threaded face in taken with the thread of the associated conduit. The organ of maneuver 30 of the horizontal conduit 26 is also engaged in the duct of the right beam 10. In each conduit 24, 26, a ball 31 is interposed between the pusher 28 and the associated operating member 30. A proximal end of the pusher 28 forming a seat for the ball 31 has a female conical shape.

To implement the method according to the invention, there are also four zirconium wedges 32, each in the shape of a rectangular parallelepiped. We arranges these four wedges 32 with the four free faces 34 of the shims 32 facing each other, so that these faces form an enclosure with a profile in parallelogram, that is to say that the enclosure is in shape of a parallelepiped. The lower wedge rests on support 8, the left wedge bears against the left spacer 20, the upper and right shims are pressed against a distal end of the pushers 28 respective.

There are optical fibers in the enclosure single-mode 36 each with a zirconium ferrule with its end, in a matrix of general shape rectangular, with rows and columns forming an angle a with the vertical direction and a angle b with the lines. Ferrules are generally in contact with each other. The four faces sides of the matrix are in contact with the four sides 34 of the enclosure.

To adjust the dimensions of the matrix, we actuates the operating member (s) 30 to make advance the push button (s) 28 towards the matrix. The matrix is thus compressed vertically following the columns between the upper wedge and the wedge lower, and / or horizontally along the lines between the left and right wedges. If applicable, this compression brings ferrules into contact not initially.

At this point, the angle b, indicating the perpendicularity of the matrix, is generally very different from 90 °. Using micrometric screws 18, we rotates the beams 10 around their ends lower 12 to the left or to the right for modify the angle of the beams relative to the base 4, the two beams 10 continuing to form a parallelogram. This change of position is reflected on the matrix fibers via spacers 20, 22, the right pusher 28 and the left and right shims 32. The change of position of the beams 10 deforms the profile into enclosure parallelogram, which varies the angles a and b of the matrix. So we can adjust the angle b to get as close as possible to a value of b equal at 90 °, as in Figure 4.

When the angle b of the matrix and its dimensions have been properly adjusted, a resin is injected molding in the enclosure and the die to mold the matrix and immobilize the ferrules relative to each other to others.

Ferrules and shims are made of zirconium with very high manufacturing tolerances weak but fully compatible with know-how industrialists. On the ferrules, these tolerances are 0.5 µm on the outside diameter, 1 µm on the inner diameter and the concentricity between the inside and outside diameters is less than 1 µm. The flatness of the shims 32 is less than 0.1 μm.

The use of beams 10 connected to the base 4 by flexible connections 12 eliminates the problem specific to mechanical parts operating clearance. The device provides perpendicularity adjustment b with a definition of 0.1 milliradian.

An 8x8 matrix (64 fibers) was produced according to this procedure. The results correspond to forecasts. The average deviation from a grid of reference is 1.04 µm, the maximum deviation is 2.55 µm, and the standard deviation of 0.58 µm. The experience acquired during the realization of this matrix (as well as a bar sixteen fibers with a maximum deviation of 1 µm per relative to the perfect position) allows to consider the production of larger dies.

This collective assembly process is simple, this which makes it possible to obtain a very low production cost. he a priori there is no limitation of the number of fibers for the realization of these matrices.

Claims (16)

Method for manufacturing optical fiber arrays (36), characterized in that it comprises the steps consisting in: arranging the optical fibers (36) in an enclosure in the form of a deformable parallelogram, in a matrix comprising lines and columns forming an angle (b) with respect to the lines; and deform the enclosure to vary the angle (b). Manufacturing method according to claim 1, characterized in that it comprises the step of fixing the fibers (36) relative to each other. Manufacturing method according to claim 2, characterized in that the fixing step comprises a molding using a resin. Manufacturing method according to any one of claims 1 to 3, characterized in that it includes the step of pressing the next die at least a direction among the direction of the lines and the direction of the columns. Device for manufacturing fiber matrices optical, having four faces (34) defining a enclosure suitable for receiving optical fibers (36) arranged in a matrix, the faces (34) giving to the enclosure a form of parallelogram, the faces (34) not parallel to each other forming an angle (b), characterized in that the enclosure is deformable for vary the angle (b). Device according to claim 5, characterized in that it comprises means (10, 14, 18) for adjusting of angle (b). Device according to claim 5 or 6, characterized in that it has two elements (32) forming two faces (34) of the enclosure parallel between them, a chassis (4), and at least one actuator (10) movable relative to the chassis and connected to the elements (32) so that a movement of the actuator (10) makes vary the angle (b). Device according to claim 7, characterized in that the actuator (10) is articulated to the chassis (4). Device according to claim 8, characterized in that the actuator (10) is articulated by means of a flexible part (12). Device according to any one of Claims 7 to 9, characterized in that it comprises two actuators (10) connected to the two elements respective (32) and interconnected. Device according to any one of Claims 5 to 10, characterized in that it comprises means (28, 30, 31) for adjusting a distance separating faces (34) of the enclosure parallel between they. Device according to claim 11, characterized in that the means for adjusting the distance include an operating member (30), a pusher (28) to push one of the faces (34) under the effect of a solicitation by the operating member, and a ball (31) interposed between the operating member and the pusher. Device according to any one of Claims 5 to 12, characterized in that it comprises zirconium elements (32) forming the faces (34). Device according to claim 13, characterized in that the elements (32) include wedges. Optical fiber matrix (36), characterized in that it was produced by a process according to any one of claims 1 to 4. Matrix according to claim 15, characterized in that the fibers (36) are single-mode.

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